A large wavelength selective switch (WSS) can be complex and costly to design and construct. Multiple smaller WSSs can be lower in cost than one equivalently sized large WSS. A known method of creating a larger WSS device from multiple smaller, WSS devices involves daisy chaining or cascading smaller WSS devices to create a larger WSS device.
For example, an 11×1 WSS can be created by cascading three 4×1 WSS devices and one 2×1 WSS device. This can be accomplished by feeding an output of the first 4×1 WSS device, an output of the second 4×1 WSS device, and an output of the 2×1 WSS device into three inputs of the third 4×1 WSS device. In such an arrangement, the 2×1 WSS device, a first 4×1 WSS device, and a second 4×1 WSS device are said to be cascaded with a third 4×1 WSS device. However, when one cascades the smaller WSS devices, not all of the inputs of each of the WSS devices are available be used as inputs to the overall 11×1 WSS, as some inputs of some smaller WSS devices are used to connect one smaller WSS device to another smaller WSS device. Furthermore, some input signals to the 11×1 WSS may traverse multiple smaller WSS devices before exiting the 11×1 WSS, resulting in increased input-to-output insertion loss for those input signals.